Background: Folic acid (pteroylglutamic acid, FA), known as a water-soluble vitamin of B complex family, plays an important role in the human body. However, excess intake of FA would mask the vitamin B12 deficiency symptoms, which may lead to other health risks. Therefore, it is very important to develop a method for the sensitive and selective determination of FA in natural sources, fortified foods and multivitamin preparations.

Methods: An electrochemical sensor was fabricated for the analysis of FA, which was based on electropolymerized molecularly imprinted poly (o-aminophenol) film and reduced graphene oxide decorated with Au nanoparticles composites (rGO-AuNPs). The transmission electron microscope, cyclic voltammetry, electrochemical impedance spectroscopy and differential pulse voltammetry were utilized for the characterization of the imprinted polymer film.

Results: Under the optimized experimental conditions, the proposed sensor exhibited two distinct linear responses ranging from 0.02 to 0.8 μmol L^-1 and 0.8 to 10 μmol L^-1 towards the concentrations of FA, and the detection limit was found to be 2.8 nmol L^-1 (S/N=3). The molecularly imprinted film proposed was also found to exhibit comparatively high selectivity toward folic acid against structurally similar analogues, and the preparation of the sensor was simple and reproducible.

Conclusion: In this work, a molecularly imprinted film fabricated on an rGO-AuNPs modified electrode was developed for the sensitive and selective determination of FA. Furthermore, the method was applied to the detection of FA in infant formula milk, multivitamin tablets and blood serum sample with satisfactory results.

背景：叶酸（pteroylglutamic acid，FA）是一种水溶性维生素B族，在人体中发挥着重要作用。然而，过量摄入 FA 会掩盖维生素 B12 缺乏症状，这可能导致其他健康风险。因此，开发一种灵敏和选择性测定天然来源、强化食品和复合维生素制剂中 FA 的方法非常重要。

方法：基于电聚合分子印迹聚（邻氨基苯酚）膜和用 Au 纳米颗粒复合材料（rGO-AuNPs）装饰的还原氧化石墨烯，制造了一种用于分析 FA 的电化学传感器。利用透射电子显微镜、循环伏安法、电化学阻抗谱和差分脉冲伏安法对印迹聚合物膜进行表征。

结果：在优化的实验条件下，所提出的传感器对FA浓度表现出两种不同的线性响应，范围为0.02至0.8 μmol L ^-1和0.8至10 μmol L ^-1，检测限为2.8 nmol L ^-1 (S/N=3)。还发现所提出的分子印迹膜对叶酸对结构相似的类似物表现出相对较高的选择性，并且传感器的制备简单且可重复。

结论：在这项工作中，开发了一种在 rGO-AuNPs 修饰电极上制造的分子印迹膜，用于灵敏和选择性地测定 FA。将该方法应用于婴幼儿配方乳、复合维生素片和血清样品中FA的检测，结果令人满意。